Field of the Invention
The present invention relates to furnace equipment, especially to an aluminum melting furnace.
Description of the Related Art
In view of the increasingly urgent environmental problems and energy crisis, energy saving and emission reduction are vigorously promoted all over the world, especially for industrial furnace related fields with huge energy consumption and serious pollution. How to achieve energy-saving and emission reduction goals has become the factor that technicians in the field must consider in designing such kind of equipment.
Taking aluminum melting furnaces for example, the temperature of the flue gas at the flue gas outlet may typically reaches to about 1000-1100° C. If such high temperature flue gas is exhausted to the ambient environment without further treatment, not only energy waste but also certain level of damage will be caused to the environment. Therefore, the person in the field have been continuously searched for novel technology to reduce the temperature of the furnace flue gas, such as re-inducing the discharged flue gas into the furnace for re-combustion, or using heat exchangers in the flue gas discharge process, in order to take use of the waste heat of the flue gas. The above-mentioned measures have achieved maximum utilization of the flue gas energy, while reducing the temperature of the flue gas, thus saving energy and reducing emission pollution. In the existing waste heat recycling technology, heat exchangers made of stainless steel or carbon steel are typically provided. However, since stainless steel is relative expensive and has limited application scope; in contrast, carbon steel is not able to stand high temperature, thus the heat exchangers that are made of carbon steel will have to be switched between several heat exchangers or heat accumulation chambers, causing a complex system structure, high cost and maintain difficulty.
As disclosed in China Patent Publication No. 103123241A, an air preheater for aluminum melting furnace is comprised of silicon carbide material and an air preheater heat transferring steel pipe, with silicon carbide material lining the inner wall of the air preheater heat transferring steel pipe. To avoid burnout of the air preheater, the inner wall of the air preheater heat transferring steel pipe is lined with silicon carbide material, causing manufacture cost rising.
As disclosed in China Patent Publication No. 2035505570U, a combustion system with fast switching heat accumulation aluminum melting furnace is comprised of a furnace body, a first and a second fuel nozzles, a first and a second vent pipes, a first and a second heat reservoirs, and a first and a second inlet pipes. Wherein the first and second heat reservoirs are operate alternatively by switching between preheating state and heat accumulating state. In addition, the first and/or second heat reservoir is comprised of a first stage heat accumulating area, a second stage heat accumulating area and a precipitation area provided between the first and second stage heat accumulating area. To avoid damage to the heat reservoirs, two alternatively operated heat reservoirs are provided in such combustion system, increasing construction cost.
Therefore, all the above-mentioned technologies utilize heat exchangers to transfer heat between high temperature flue gas and air, preheating the air with the waste heat of the flue gas. However, such technologies have some drawbacks or deficiencies as follows, for example: (1) A pair of combustors and a pair of heat reservoirs that correspond to the pair of combustor are provided on two sides of the furnace body. When the temperature of the combustor and heat reservoir located on one side is too high, the combustor and heat reservoir located on the other side will be switched on. However, it is required to stop running the devices in such switching process, causing discontinuous combustion and high power consumption; (2) The heat exchange rate of the above heat transfer mode is insufficient to achieve satisfactory heat exchange effects. In particular, as for aluminum melting furnaces, since the temperature of the discharged flue gas may be up to 1000-1100° C., neither the structure nor the operating mode of the above heat exchangers can meet the requirement of effectively reducing the flue gas temperature. Thus, the heat exchangers tend to be overheated. Especially for those heat exchangers that are made of carbon steel, they are unable to stand such high flue gas temperature, causing potential safety hazard; (3) The content of nitrogen oxide in the discharged flue gas is so high that it may cause damage to the environment.
Therefore, it is in urgent need in the field to provide an aluminum melting furnace waste heat utilization system that is able to take full use of flue gas waste heat and achieve the effective heat exchange between high temperature flue gas and air.